Led fluorescent tube replacement light with reduced shock hazard

ABSTRACT

An LED-based tube light suitable for replacing a conventional 48-inch fluorescent tube light includes LEDs connected into a complete illumination circuit that runs exclusively through connectors at one end of the light. In an alternative embodiment, two LED groups are used, each group being connected exclusively to its own set of end connectors.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional patentapplication Ser. No. 61/421,343 filed Dec. 9, 2010

BACKGROUND

Fluorescent tube light fixtures are commonly found in offices,institutions, shops, garages and many other places. A typical fixtureincludes a reflector accommodating several tube lights in parallel. Eachlight is mounted between opposed pin-type receptacles spaced, forexample, 48″ apart to receive electrically joined bi-pin connectorsfound on opposite ends of conventional fluorescent tube lights. Thelights are sometimes installed into the fixture receptacles one end at atime, albeit one can insert both ends of the tube into the fixturereceptacles at the same time.

LED-based replacement lights are now available for fluorescent tubelights and can be installed or plugged into fixtures normally intendedfor conventional fluorescent tube lights, usually after removal of theballast. Because the LEDs and other components within some LED-basedreplacement lights provide a complete circuit from the pins on one endof the tube to the pins on the other end of the tube, a shock hazardexists if a person installs such a replacement light in a “hot” featureone end at a time; i.e., after installing the pins at one end into thereceptacle of a hot fixture, one can receive a shock if one touches thepins at the other end.

SUMMARY

Disclosed herein is an LED-based, fluorescent tube replacement lightthat reduces or eliminates the risk of shock in the circumstancesdescribed above; i.e., installing an LED-based replacement light intothe fixture originally designed for a double-ended fluorescent tubelight having pin-type connectors. In general, the lights disclosedherein establish a complete electrical circuit through some or all ofthe LEDs in the light from only one end of the light, therebyelectrically isolating the pins on one end of an LED-based replacementlight from the pins on the other end of the replacement light, such thatno complete electrical circuit between the two ends exists.

In one form, this can be accomplished by connecting all of the circuitcomponents including the LEDs themselves between the pills at only oneend of the light while the pins at the other end of the light serve onlyto provide a mechanical anchor; i.e., the pins at said other ends areelectrically deadened so that they are not in circuit with the pins atthe opposite end. The pins that are connected in circuit with the LEDsmust, of course, not be directly tied together as they are inconventional bi-pin connector installation.

In another embodiment disclosed herein, the electrical componentsincluding the LEDs within a replacement light can be divided intogroups, which groups are arranged in their own circuits and have theirown end connectors. For example, one LED circuit may have its connectorsat the left end of the tube while the other LED circuit has its pins atthe right end of the tube.

Variations on these arrangements are possible. For example, one of morepulse-width-modulation power supplies may be incorporated into thelight.

BRIEF SUMMARY OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views and wherein:

FIG. 1 is a sectional view through a normally ballasted fixture whichhas been modified to receive an LED-based fluorescent tube replacementlight wherein only the left end of the fixture is hot and the right endof the fixture serves only as a mechanical anchor for the tube light;

FIG. 2 is a sectional view of an alternative embodiment in which theelectrical circuitry within the LED-based replacement tube light isdivided into separate groups, which groups include LED banks which areelectrically isolated from one another; and

FIG. 3 is a perspective view of another embodiment representing avariation in the arrangement of LEDs.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

Referring to FIG. 1, there is shown a fixture 10 which is normallyballasted and otherwise configured to receive a fluorescent tube lighthaving bi-pin connectors at opposite ends. Here, a conventionalfluorescent tube has been replaced with an LED-based light 22. The term“bi-pin” connector refers to a set of two small conductive pins arrangedin parallel and serving to make electrical contact between a source anda circuit on-board the light. These connectors also serve as mechanicalanchors for the light to which they are attached. In a conventionalfluorescent light, the two pins at each end are electrically tiedtogether by a metal conductor. In the embodiments disclosed herein, thetwo side-by-side pins are not electrically tied together.

The fixture 10 comprises opposite end receptacles 12, 14, each havingconductive pin receivers 16 a, 16 b spaced apart to receive the pins 28a, 28 b and 30 a, 30 b of the LED-based replacement light 22. Thefixture 10 may be of the twist-to-lock type where the light 22 is turned90° to lock it into the fixture.

In FIG. 1, the fixture 10 has been modified by removing the ballast andbreaking any electrical tie such as is seen at 18 between the pins 16 a,16 b so that they may be and are electrically isolated from one another.In this configuration, pin 16 a is the hot pin as connected to the hotside of 110V AC line source 20 while pin receiver 16 b is grounded. Inthis embodiment, the pin receivers 16 a, 16 b in the right sidereceptacle 14 are electrically deadened; i.e., they are not wired to anyelectrical source. A label 17 may be placed on the receptacle 12 toidentify the hot pin. A similar label 19 is placed on the light 22 nearthe hot pin 28 a.

In FIG. 1, the LED-based tube light 22 is shown to comprise pins 28 a,28 b on the left side and pins 30 a, 30 b on the right side, these pinsbeing configured so as to be virtually identical in size and spacing tothe pins found on a conventional fluorescent tube light. The pins areshown in FIG. 1 to be integrated with end caps 24, 26 which are mountedto and secured over a glass envelope 27 in conventional fashion.

Disposed within the translucent envelope 27 are a rectifier/regulatormodule 32, a filter module 34 and a bank of LEDs 36 which, when suppliedwith current from the rectifier/regulator and filter 34, produceillumination through at least part of the glass envelope 27. Theenvelope 27 may also be made of other translucent materials, includingplastic. The LEDs may be distributed along a heat sink or other support.The regulator 32 is preferably a current limiter of the pulse widthmodulation (PWM) type as described in U. S. Pat. No. 7,049,761 theentire content of which is incorporated herein by reference. PWMregulators may be used not only for current limiting but also forbrightness control and selective dimming.

As seen in FIG. 1, the LEDs 36 and all associated circuitry arecompletely isolated from the pins 30 a, 30 b in the receptacle 14.Moreover, pins 30 are electrically dead. A dielectric medium 37, in thiscase air, exists between the left and right pin sets 28, 30.Accordingly, even if the installation process involves plugging in thepins 28 a, 28 b to a hot source first, there is no risk of shock if oneinstalling the tube touches the pins 30 a, 30 b in the installationprocess. The LEDs may be of any of the available types, includingsoldered lead LEDs and surface mount LEDs.

Looking now to FIG. 2, there is shown a fixture 40 which is identical tothe fixture 10 of FIG. 1 except for the fact that the receptacle 14′ onthe right side of the fixture as shown in FIG. 2 is wired to an ACsource 21 and both sources have switches S. The pin receivers 16 a, 16 bare the same as those found in the receptacle 10 of FIG. 1; note thatany electrical short circuit between the pins on either end which waspreviously used to tie them together has been eliminated, so pinreceiver 16 b can be grounded while pin 16 a is hot.

Disposed within the fixture 40 is an LED-based fluorescent replacementtube light 41 which is substantially similar to the light 22 of FIG. 1except that it is double-ended; i.e., in addition to the LED group orbank 36, a second LED group or bank 48 is provided in the right side ofthe tube 42. The LEDs 48 are wired to the pins 30 a, 30 b along with arectifier circuit 44 and a filter circuit 46. When supplied with currentby the filter 46, the LEDs 48 produce illumination similar to thatproduced by LEDs 36. Again, the left and right sides of the tube light42 are electrically isolated by a dielectric medium 38, including air.Again, plugging in one end of the light 42 poses no electrical shockhazard associated with touching the pins at the opposite end of the tubesince the left and right pin sets 28, 30 are electrically isolated fromone another.

It will be understood that the embodiments shown here are illustrativeand various modifications and additions to them are possible within thespirit and scope of the invention as defined herein. For example, theLED groups 36 and 48 in the embodiment of FIG. 2 need not be arrangedleft and right as shown, but may be interspersed over the entireavailable length of the light 22 as shown in FIG. 3; for example, onegroup can be illuminated independently of the other, but either groupalone will effectively illuminate the entire effective length of thelight albeit at a lesser illumination level. Again, the regulators 32and 46 are preferably PWM type regulators as described above.

FIG. 3 shows a tube light 50 including a cylindrical glass or plasticenvelope with end caps 52, 54 at the opposite ends thereof. End cap 52provides a mount for conductive pin connectors 56 and end cap 54provides the same for connectors 58. A circuit board 60 is mountedwithin the translucent envelope and extends from one end cap to theother. Although the envelope is described as cylindrical, it is to beunderstood that the light 50 may also be constructed in the form of anextruded metal half-cylinder to which a half-cylinder glass or plasticlens is attached. In that case, the extrusion receives the board 60 andserves as a heat sink.

Diodes 62 are arranged on the board 60 in staggered fashion andconnected in series between pins 56. Diodes 64 are also arranged instaggered fashion and connected in series between pins 58. Since the twodiode circuits are separate, they may be turned on and off separately byswitches S. Alternatively, switches S (FIG. 2) may be ganged together orotherwise arranged as a single switch so both banks of LEDs go on andoff together. Although not shown, PWM regulators may be mounted on boardlight 50 if desired or be wired off board for dimming purposes. Again,LEDs 62, 64 may be of any available type but are preferably white formost institutional applications.

1. An LED-based tube light for replacing a conventional fluorescent tubelight in a fixture designed to receive a conventional light with bi-pinconnectors comprising: a tubular body having opposite ends; a pluralityof LEDs disposed within the body between said ends; a pair of connectorpins at each end of the light; said LEDs being electrically connected incircuit to only one of said pin pairs; and a PWM regulator in theelectrical circuit with said LEDs.
 2. An LED-based tube light forreplacing a conventional fluorescent tube light in a fixture designed toreceive a conventional tube with bi-pin connectors at each endcomprising: a tubular body having opposite ends; a first group of LEDsdisposed within said body and connected into a first circuit; a firstset of connector pins at one of said opposite ends and connectedexclusively into said first circuit; a second group of LEDs disposedwithin said body and connected into a second circuit; and a second setof connector pins at the other of said opposite ends and connectedexclusively into said second circuit; wherein said first and secondcircuits are electrically isolated from one another.
 3. A light asdefined in claim 2 wherein said body includes a translucent envelope. 4.A light as defined in claim 2 wherein each of said first and secondcircuits includes a PWM regulator.
 5. A light as defined in claim 2wherein each of said first and second circuits includes a switch.
 6. Alight as defined in claim 2 wherein said body is approximately 48 incheslong.